Rotary bell cup atomizers are commonly used in coating operations such as, for example, the painting of vehicle body parts. These coating operations are carried out, in the main, by either robotically mounted and controlled atomizers or by hand-held spray gun atomizers. Both coat various work-pieces by operation of bell cup rotating atomizers affixed thereto.
Rotary atomizers are used in liquid based paint coating operations and bell cup rotary devices are also used in powder coating operations. The invention herein described and claimed is useful in both types, either robotically or machine mounted, or applied via hand held spray gun.
Rotary atomizers which are used in coating the various substrates employ centrifugal forces generated by a rotating bell cup to atomize paint supplied thereto. Pressurized air is directed as an axially-extending shroud around the atomized paint and controls the disposition of paint particles on the work-piece. Electrostatic charging may be used to assist in attracting the atomized particles to the substrate, all of which is known.
Examples of rotary bell cup atomizers are found in prior patents of one of the named inventors herein, specifically in U.S. Pat. Nos. 7,056,397, 6,676,049, and 6,341,734.
Rotary bell cups for atomization are precision instruments, their outer, atomizing edges requiring absolutely flawless precision in order to ensure the flaw-free coating of such substrates as automobile body parts. Imperfections in the coating, termed “dirt” in industry parlance, are unacceptable generally and costly to correct when they do occur. A bell cup having its razor-thin knife edge is highly susceptible to any outside forces acting thereon and producing dings or chips in this fragile edge. While precise movements or robotically controlled atomizers is somewhat less susceptible to damaging nicks and dents than are hand-held spray guns, for obvious reasons, both types of apparatus can and do incur damaging accidental dings and dents during coating operations, the practical result of which can be disastrous to the operation and/or the safety of the operator, requiring complete shutdown, replacement of the damaged cup, and possible discarding or reworking of the flawed work-piece.
The present invention is directed to preventing just such a catastrophic operational event by providing a rotary bell cup atomizer having a protective cover for its atomizing edge, which cover is actuated and extends over the cup edge during idle operation, thereby protecting the edge from external forces during idle, and which retracts to uncover the edge simultaneously with the start of a coating operation, allowing the coating to proceed as normally. On cessation of coating, the cover again extends over the cup edge to protect it.